Oncologic safety of breast conserving surgery after tumour downsizing by neoadjuvant therapy: a retrospective single centre cohort study.

The objective of this study is to analyse local recurrence rates in patients receiving neoadjuvant chemotherapy (nCT) comparing mastecomized (MX) patients with those undergoing breast conserving therapy (BCT). Patients undergoing breast cancer surgery after nCT (3xCMF or 3-6xED) between 1995 and 2007 at our department were retrospectively analysed. The median follow up was 60 months for 308 patients. Patients who were downsized from MX to BCT with partial or complete response (n = 104) had a similar local recurrence free survival (LRFS) compared to patients who did not experience successful downsizing (n = 67) and finally undergoing MX (LRFS MX-BCT 81% vs. MX-MX 91%; P = 0.79). Uni- and multivariate analyses demonstrated that BCT itself was not an independent prognostic factor for a worse LRFS (P = 0.07 and 0.14). After no pathologic change or progressive disease the risk of local recurrence was increased in patients undergoing BCT (MX-BCT; n = 6 LRFS 66%) compared with MX (n = 44; LRFS 90%; P = 0.04). Overall survival in general was better for the BCT group (n = 197) compared with MX group (n = 111) regardless of clinical response (92% vs. 72%; P < 0.0001). Breast conservation, nodal negativity and low or medium grade histology were prognostic factors for an improved OS (P = 0.02, 0.01, 0.004). In conclusion, our study suggests that BCT is oncologically safe after tumour downsizing by nCT in patients primarily scheduled for mastectomy. These patients, however, should not be treated with breast conservation in the absence of any proven response after nCT.